Risk of Preeclampsia, Gestational Hypertension, and Adverse Pregnancy Outcomes Associated With Stage 1 Hypertension Before 20 Weeks Gestation for the Period 2016- 2019 at Kenyatta National Hospital -a Retrospective Cohort Study

Abstract

Background: The American College of Cardiology/American Heart Association’s (ACC/AHA) guidelines for hypertension were updated in 2017. The 1988 guidelines of 140/90mmHg blood pressure were revised downwards to 130/80 mmHg blood pressure. Even with this change, the cut-off for hypertension for the obstetric population of Kenya has remained unchanged at 140/90mmHg. With hypertension defined as 130/80 mm Hg blood pressure, the diagnosis of preeclampsia and adverse pregnancy outcomes such as small for gestation are lower than when hypertension is defined as 140/90mmHg, although data from Africa is limited. Objectives: To determine the association between stage 1 hypertension before 20 weeks gestation and risk of preeclampsia, gestational hypertension, and adverse pregnancy outcomes at Kenyatta National Hospital from January 2016 to December 2019. Methodology: This was a retrospective cohort design in which the adverse maternal, fetal, and neonatal outcomes were compared for two groups. The groups comprised those who had their blood pressure taken before the 20th week of gestation, with the exposed group defined as women with stage 1 hypertension (130-139 mm Hg SBP or 80-89 mm Hg DBP while nonexposed group comprised normotensive women (<130 mm Hg SBP and <80 mm Hg DBP) before 20th week of gestation. The study was conducted at Kenyatta National Hospital (KNH), which is a tertiary teaching and referral facility. Analysis was done using Statistical Package for Social Scientists Software (SPSS) version 25. Results: A total of 589 files were accessed with 292 (146 exposed and 146 for the nonexposed) meeting the inclusion criteria. The baseline characteristics for the two groups were highly comparable with minimal differences.For thosee with stage 1 hypertension (exposed group), the majority were aged between 31 – 35 years (32.2%, N = 47) while the majority of the nonexposed group (normotensive mothers) were aged between 26 – 30 years (34.9%, N = 51). In the normotensive mothers, 1.4% (N = 2) were teens, but the exposed group had no teenage mothers. In both groups, the majority of the women were married/cohabiting with 92.5% (N = 135) exposed versus 95.9% (N = 140) nonexposed group. On education, the majority of those with stage 1 hypertension had the highest education at college/university 45.9% (N = 67) while only 0.7% (N = 1) had no formal education. All the normotensive women had formal education with the majority having secondary or College/university (42.5%, N = 62) each. On occupation, the majority of the exposed group and the same to nonexposed were employed 69.2% vs. 71.2%. The majority of the mothers in either group resided in urban areas (87.7% vs. 85.6%) for the exposed and nonexposed respectively. In both groups, there were histories of miscarriage as indicated by higher percentages of those who had been pregnant 5 or more times 18.5% (N = 27) for the exposed and 17.1% (N = 25) for the nonexposed group. Those who progressed to develop pre-eclampsia were 32.9% (N = 48) for the exposed group and 6.8% (N = 10) nonexposed group. The risk of developing pre-eclampsia was 4.8 times higher for those with stage one hypertension compared to the normotensive mothers (RR = 4.8, 95% CI: 2.53 – 9.12 p < 0.001). The frequency of gestational hypertension was 13.7% (N = 20) for the exposed group and 4.8% (N = 7) for the nonexposed group. Adverse pregnancy outcomes (both maternal and perinatal outcomes) were higher for the exposed group than the nonexposed group. However, Stage 1 Hypertension increased the risk of pre-eclampsia by 8.7 folds (aRR = 8.754, 95% CI: 4.344 – 25.118, p < 0.001), increased the risk of gestational hypertension by 4.5 folds (aRR = 4.530, 95% CI: 2.223 – 19.183, p = 0.001), and increased the risk of placenta abruption by 3 folds (aRR = 3.161, 95% CI: 1.231 – 8.118, p = 0.017). There was no statistically significant association between the adjusted risk ratio with the gestational diabetes mellitus (aRR = 1.956, 95% CI: 0.648 – 5.900, p = 0.234) and CS delivery (aRR = 2.329, 95% CI: 0.997 – 5.442, p = 0.051). Regarding perinatal outcomes, there was no statistically significant association with the adjusted risk ratio for the perinatal outcomes apart from that of composite perinatal outcomes (aRR = 4.437, 95%CI: 1.336 – 14.735, p = 0.015). The adjusted risk ratio indicated that the risk of having at least one adverse perinatal outcomes investigated in this study was multiplied by 4.4 times for the mothers with stage 1 hypertension at the early gestation stage in comparison to normotensive mothers. The other perinatal outcomes, which had no statistically significant adjusted relative risk were preterm birth (aRR= 0.524, 95% CI: 0.176 – 1.555, p = 0.524), small for gestation (aRR = 0.767, 95% CI: 0.272 – 2.157, p = 0.615), stillbirths (aRR = 2.132, 95% CI: 0.579 – 7.854, p = 0.255, and early neonatal death (aRR = 1.350, 95% CI: 0.310 – 5.873, p = 0.689) Conclusion: Stage 1 hypertension is often ignored as a borderline or early hypertension incidence with most patients underrating the impact it might have on pregnancy outcomes. This study has demonstrated that Stage 1 hypertension can have far-reaching implications, such as pre-eclampsia, gestational hypertension, placenta abruption and composite perinatal outcomes, which in turn could trigger a cascade of pregnancy complications. The risks should, therefore, attract the attention and seriousness of healthcare workers and patients alike to enable appropriate interventions to be taken well in advance to reduce adverse pregnancy outcomes.